This invention concerns a device to produce multi-layer electronic circuits consisting of a plurality of elementary circuits, each made on a base support consisting of very thin sheets of alumina and plastic materials, commonly known as xe2x80x9cgreen-tapexe2x80x9d.
The device according to the invention is able to process, in a completely automatic fashion, sheets of green-tape, already cut to measure according to the final destination of the multi-layer circuit to be produced, to perform three operations: to deposit the conductor material by means of serigraphy on each base support, the drying operation in the oven, and also the cooling operation. An assembly station is provided to stack several layers of electric circuits and connect them electrically with each other to achieve multi-layer circuits.
One of the techniques well-known in the production of multi-layer electronic circuits is to use, as base supports for the individual circuits, one or more sheets of insulating material, consisting of alumina or synthetic materials, according to the green-tape technology.
The green-tape supports are normally arranged on rectilinear guides along which they are fed in sequence, by means of a feed mechanism, from a loading station to a printing station where, by means of serigraphy, the conductor material is deposited thereon, in the form of a conductor paste, according to a pre-defined mask. Subsequently, each support is introduced into a drying oven, where it is kept at a temperature of at least 120xc2x0 C. for the time needed to make the conductor paste set, which time at present is at least ten minutes.
After the drying operation in the oven, the supports are cooled in a suitable cooling chamber and then discharged from the device.
To make up the multi-layer circuits an independent device is used where the individual electronic circuits are superimposed and welded to each other with possible intermediate layers of insulating material, similar to the green-tape base supports.
In the state of the art, therefore, it is necessary to move the individual electronic circuits to transfer them from one device to the other, using specialized staff, with a consequent loss of time and increase in production costs, and a risk of damage during transport and handling.
Moreover, if we consider that the time needed to perform a single serigraphy operation on a base support is about 10 seconds, we can see that the hourly production of conventional devices is about 360 elementary circuits. As a consequence, since the length of each support is some tens of centimeters, the average speed of feed of the supports along the rectilinear guides is about 1-1.5 m/min.
It is difficult to overcome such limits with conventional devices, also because each elementary circuit, after being serigraphed, as we have seen, must stay inside the drying oven for at least 10 minutes.
Consequently, the development of the line inside the drying oven may be even more than 10 meters.
The state of the art includes devices with a linear-type drying oven, more than 10 meters long, with consequent disadvantages from the point of view of bulk, and also devices where the drying oven develops partly upwards. In this latter type, there is a conveyor belt system inside arranged in a coil, on which brackets are attached; on each bracket one or more supports to be dried are rested. This second solution has the disadvantage that it is both complex and expensive, and requires that the supports which are to be dried are handled, in order to arrange them on the brackets of the oven and to remove them therefrom.
The present Applicant has devised and embodied the device to produce multi-layer electronic circuits according to the invention to overcome these shortcomings.
The device to produce multi-layer electronic circuits according to the invention is set forth and characterized in the main claim, while the dependent claims describe other innovative characteristics of the invention.
One purpose of the invention is to achieve a device to produce multi-layer electronic circuits which will permit the performance of all the different manufacturing operations in a completely automatic manner: from picking up each individual blank base support to superimposing the individual electronic circuits, passing through the stages of depositing the conductor paste on every individual base support, and the drying and cooling steps.
In accordance with this purpose, the device according to the invention, to produce multi-layer electronic circuits consisting of a plurality of individual circuits each made on a base support on which electrically conductive material is deposited, able to embody determined conductor tracks, comprises at least a printing station able to deposit the electrically conductive material onto the base support and a drying and cooling station, downstream of which there is an assembly station able to superimpose one on top of the other a plurality of base supports on which individual electronic circuits are made, selectively alternating with electrically insulating sheets.
Another purpose of the invention is to achieve a device to produce multi-layer electronic circuits which will allow to obtain high productivity, at least double that of conventional devices, at the same time ensuring excellent quality.
In accordance with this purpose, the printing station comprises at least two printing units arranged laterally with respect to feed means to feed the base supports and able to deposit the electrically conductive material onto the base supports in an autonomous fashion with respect to each other.
According to another characteristic of the invention, stacking means are provided to stack the base supports one on top of the other, after they have been processed in the printing station, so that they can be introduced in vertical piles into the drying and cooling station, and spacer means are provided to keep the base supports separate from each other when they are stacked up.
According to another characteristic of the invention, the assembly station comprises first pick-up means able to selectively pick up each electrically insulating sheet and each base support on which an individual electronic circuit is made, and to position them alternately in a single reference position.
In accordance with another characteristic of the invention, the assembly station also comprises a centering board, able to move along the two horizontal axes (x and y), orthogonal to each other, and to rotate on the horizontal plane with respect to a vertical axis z (rotation xcex8); translation means are provided to translate the base supports and the electrically insulating sheets from the reference position to the centering board.
In accordance with another characteristic of the invention, the assembly station also comprises an automatic welding device mounted downstream of the centering board and able to weld the individual electronic circuits together to achieve a multi-layer circuit.
In accordance with another characteristic of the invention, the drying and cooling station comprises a plurality of drying modules, adjacent to each other, and each having a drying chamber inside which at least one pile of base supports is able to be inserted, and means to circulate a current of hot air in a direction transversal to the pile, so that a plurality of base supports, with the relative electronic circuits deposited thereon, can be dried simultaneously.
According to another characteristic of the invention, the drying and cooling station comprises a cooling unit through which each pile of base supports is fed in such a manner that it can be lapped by a current of cold air, in a direction transversal to the pile, so that a plurality of base supports, with the relative electronic circuits deposited thereon, can be cooled simultaneously.
According to another characteristic of the invention, first linear feed means for the base supports are provided to feed the base supports, one in front of the other and separated by a determined distance d, from a loading station towards the stacking means, passing adjacent to the printing station; second linear feed means are provided to feed the piles of base supports, one in front of the other and separated by the same distance d, from the stacking means to the assembly station through the drying and cooling station.
According to another characteristic of the invention, the printing station is displaced laterally with respect to the first linear feed means of the base supports, and transverse feed means are provided to move the base supports transversely, one at a time, from the first linear feed means to the printing station and vice versa.
According to another characteristic of the invention, the base supports are first stacked up, subsequently deposited one next to the other to be fed in series, one after the other, towards the printing station; then they are again stacked up to be introduced into the drying and cooling station and finally again fed serially, one after the other, to the assembly station.
According to another characteristic of the invention, the device is able to manage advantageously other base supports of a flexible type, for example of the green-tape type. In order to do this, the spacer means comprise a rigid supporting plate for each base support, on the upper surface of which a base support is able to be rested.